l3backend: adding new DVI specials?

[Joseph Wright]

On 13/02/2020 22:59, Karl Berry wrote:
>           \special{header=l3backend-dvips.pro}
> 
> I admit I don't understand. So this \special is output unconditionally?
> How about only emitting this \special if the backend is in fact dvips,
> instead of expecting every other DVI driver in the world to be changed
> to recognize it? (Especially when it's merely to be ignored.) I'm sure
> you thought of this, but ... I don't understand. --thanks, karl.
> 

Hi Karl,

A "latex" run *cannot* know what the driver is unless it's told: you 
have to make some kind of guess. That's in contrast to pdflatex, 
xelatex, lualatex where we can know.

If one goes down the route of explicitly requiring a driver option in 
all cases, the basic case of 'no option at all' works with zero drivers. 
The graphics package has for years assumed no option -> dvips, and 
dvipdfmx users are thus accustomed to having to specify it. It's hard to 
see another way to try to being work on making new PDF-focussed features 
work in LaTeX output.

Joseph